In recent years, the projector market has been growing rapidly, along with the use of personal computers. Liquid crystal display elements of the transmission-type and the reflection-type and DMD display elements that include micro mirrors in an orderly array are known display elements that modulate light in order to produce image light signals. Projection display devices using such display elements include front projection devices that project personal computer images and rear projection devices that project television images.
In such projection display devices, the projected images may have various common aspect ratios. For example, aspect ratios of 4:3 or 16:9 are popular for television images, and accordingly, display elements are generally manufactured with effective pixel regions having one of these two aspect ratios.
When an aspect ratio is required that is different from the two common ones described above, it is known to change the aspect ratio of the light beam modulated by the display element by, for example, using an anamorphic lens in the projection optical system as described in Japanese Laid-Open Patent Applications H07-333497 and 2002-258154. However, the use of an anamorphic lens tends to enlarge the optical system. Moreover, the use of such a lens also tends to increase the production costs and to decrease the optical performance when projecting an image.
When a projected image having an aspect ratio other than the two common ones described above is required, it is not practical in terms of manufacturing costs to manufacture display elements with appropriate aspect ratios that meet the demands of individual requests relating to the size and the number of pixels. Therefore, a low-cost, compact projection display device that allows for the use of generally available display elements, as described above, with their usual aspect ratios is demanded.